P0633

What it means

P0633 means the engine control module has detected that the immobiliser key in use has not been programmed to it. The ECM checks the transponder or key code during the start sequence and, if it cannot match it to the learned keys stored in memory, it sets the code. The engine may be prevented from starting or running as a result.

Symptoms

• Engine cranks but will not start
• Engine starts then stalls after a second or two
• Immobiliser or security warning light on or flashing
• No crank on some vehicles
• Spare or newly cut key does not work while the original does
• Fault appeared after ECM replacement or battery disconnection

Possible causes

• Key not programmed or learned to the ECM, such as a new or spare key that has not been registeredlikely
• Replacement or second-hand ECM fitted that has not been matched to the vehicle's immobiliser systemlikely
• Faulty or damaged key transponder chippossible
• Faulty immobiliser antenna or coil around the ignition barrel, or its wiring or connectorpossible
• Low battery voltage during the start sequence corrupting the key recognitionpossible
• Corrupted key data or software fault in the ECM or immobiliser modulerare

How to diagnose

1. Read all stored codes and freeze frame data, and note whether other immobiliser or body control module codes are present
2. Try every available key, including the original, and note which ones work and which do not
3. Check the battery condition and charging voltage, and rectify any low voltage before further testing
4. Inspect the key for damage and the ignition barrel antenna wiring and connectors for damage, corrosion or looseness
5. Observe the immobiliser warning light behaviour with the ignition on and compare it with the manufacturer's specification for the model
6. Check the immobiliser and ECM communication on the data bus and confirm the ECM is responding
7. Check the vehicle history for recent ECM, key, battery or immobiliser work, as procedures vary by make and model

How to fix

• Programme or register the key to the vehicle using the correct procedure for the make and model, which may require security access
• Match or adopt the replacement ECM to the immobiliser system, or fit an ECM correctly prepared for the vehicle
• Replace a faulty key or transponder and programme the new key
• Repair or replace the faulty immobiliser antenna, wiring or connector
• Restore battery health or replace the battery, then repeat the key learning procedure

Can I keep driving?

Nearby codes

• P0632GenericOdometer Not Programmed - ECM/PCM
• P0634GenericControl Module Internal Temperature A Too High